1951 American Helicopter, XH-26, Jet Jeep, 50-1841
Two 6.75-inch XPJ49 pulse jet engines, 35 pounds of thrust each,
The pulse jets produced an unacceptable amount of noise. The drag of the engines prevented autorotation landing as the rotor blade would not spin freely.
Only five built
US Air Force Museum, Dayton, OH, Oct 2016